The present invention relates to semiconductor processing in general and in particular to a process for repairing pinhole defects in patterned resist coatings.
In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there have been, and continue to be, efforts toward scaling down device dimensions on semiconductor wafers. In order to accomplish higher device density, smaller and smaller features sizes are required. These may include the width and spacing of interconnecting lines, spacing and diameter of contact holes, and surface geometry of corners and edges of various features.
High resolution lithographic processes are used to achieve small features with close spacing between adjacent features. In general, lithography refers to processes for pattern transfer between various media. Lithography is a technique used for integrated circuit fabrication in which a silicon slice, the wafer, is coated uniformly with a radiation-sensitive film, the resist. The film is selectively exposed with radiation (such as optical light, x-rays, or an electron beam) through an intervening master template, the mask, forming a particular pattern. Areas of the coating exposed through the mask become either more or less soluble (depending on the type of coating) in a particular solvent developer. The more soluble areas are removed in a developing process leaving the less soluble areas in the form of a patterned coating.
One type of defect that may occur in a patterned resist coating is a pinhole defect; a hole through the coating that may be only a few microns across. Pinhole defects may result from non-uniformities in the resist coating and preparation process, defects in the mask used to expose the resist, or non-uniformities in the developing process. Very thin resist coating are particularly vulnerable to pinhole defects. These defects may lead to problems, such as current leaks, in the finished device. There is an unsatisfied need for a process for repairing pinhole defects.
According to one aspect of the present invention, pinhole defects in resist coatings are repaired by heating the resist briefly to induce the resist to flow and fill pinholes. The resist is brought to a temperature at or above that at which the resist flows for long enough to permit the resist to flow and fill pinhole defects, but not so long as to corrupt the resist pattern. The original resist pattern may be biased to allow for some flow during the pinhole repair process. The entire patterned resist may be heated at once, or it may be heated one portion at a time. The application of heat may optionally be limited to locations where pinhole defects are found. By means of the invention, very thin patterned resist coatings free from pinhole defects may be obtained
In one aspect, the invention provides a system for repairing pinhole defects in a patterned resist coating on a substrate, the system including a heating device that heats the resist in a controlled manner causing the resist to flow sufficiently to close pinhole defects while substantially preserving the resist pattern.
In another aspect, the invention provides a system for repairing pinhole defects in a patterned resist coating on a substrate, the system including means for heating the resist in a controlled manner to cause the resist to flow sufficiently to repair the pinhole defects
In another aspect, the invention provides a method of processing a substrate with a patterned resist coating having pinhole defects including the step of applying sufficient heat to the resist to cause the resist to flow and thereby close one or more pinhole defects in the resist coating.
In another aspect, the invention provides a method of preparing a patterned resist coating including the steps of forming the resist into a coating with a pattern that is slightly smaller than the desired coating pattern and applying heat to the resist thereby causing it to flow until it forms the desired pattern.
In a further aspect, the invention provides a method of repairing pinhole defects in a patterned resist coating including steps for causing the resist to flow and fill the pinhole defects.
The invention extends to features hereinafter fully described and features particularly pointed out in the claims. The following detailed description and the annexed drawings set forth in detail certain illustrative examples of the invention. These examples are indicative of but a few of the various ways in which the principles of the invention may be employed. Other ways in which the principles of the invention may be employed and other objects, advantages and novel features of the invention will be apparent from the detailed description of the invention when consider in conjunction with the drawings.